arm64: abort counter_read_on_cpu() when irqs_disabled()

Given that smp_call_function_single() can deadlock when interrupts are
disabled, abort the SMP call if irqs_disabled(). This scenario is
currently not possible given the function's uses, but safeguard this for
potential future uses.

Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Will Deacon <will@kernel.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20201113155328.4194-1-ionela.voinescu@arm.com
[catalin.marinas@arm.com: modified following Mark's comment]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 7c9b6a0..b8026ec 100644 (file)
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -343,9 +343,16 @@ static void cpu_read_constcnt(void *val)
 static inline
 int counters_read_on_cpu(int cpu, smp_call_func_t func, u64 *val)
 {
+       /*
+        * Abort call on counterless CPU or when interrupts are
+        * disabled - can lead to deadlock in smp sync call.
+        */
        if (!cpu_has_amu_feat(cpu))
                return -EOPNOTSUPP;
 
+       if (WARN_ON_ONCE(irqs_disabled()))
+               return -EPERM;
+
        smp_call_function_single(cpu, func, val, 1);
 
        return 0;